[swb85]

Mine does the same thing and so does my buddy's '85......and while I haven't had time to determine the cause/fix, I'll place my bet on this: Remove your glove box door and you'll see the top of the hvac "box". On top of that is a metal rod attached to a flapper door inside the "box". With your defrost running, actuate that rod with your hand and I'll bet your defrost starts to work. I haven't figured out why the door won't work on it's own (I think it's got to be a bad vacuum line/pod somewhere), maybe you can figure it out and tell me the answer so I can fix mine!